The present invention relates to a set of provisional prosthesis instrumentation, and more particularly to provisional instrumentation which is suitable for use in hip hemiarthroplasty procedures in which the proximal portion of the femur is replaced with a suitable prosthetic hip joint implant or implant assembly which will mate or articulate directly with the natural acetabulum (as opposed to mating with a prosthetic acetabular joint implant component).
Two different types of procedures are typically suitable for hemiarthroplasty procedures. One of these types is the use of a bipolar prosthesis member such as those described in U.S. Pat. No. 3,813,699 to Giliberty or U.S. Pat. No. 4,770,658 to Geremakis et al. In general, a bipolar prosthesis has an external surface which articulates with the natural acetabulum and an internal surface which articulates with the spherical head member of a prosthetic femoral component. The other of these types is often referred to as a unipolar endoprosthesis in which the prosthetic femoral component includes a spherical head member which is large enough to articulate directly with the natural acetabulum. Both of the above hemiarthroplasty procedures enable articulation with the natural acetabulum. These two procedures permit later conversion to a total hip replacement in which the acetabular portion is also replaced with a prosthetic acetabular component. With the bipolar procedure, the bipolar prosthesis is removed from the head of the hip stem, and an acetabular prosthesis implanted which mates with the head of the remaining femoral component. With the unipolar endoprosthesis, these may typically be modular (where the head is a separate component from the stem portion of the hip prosthesis). This permits the larger unipolar head to be removed and replaced with a smaller head without removing the femoral stem to enable this smaller head to mate with an acetabular prosthetic implant component
Various types of provisional or trial prosthesis instrumentation are typically used in a femoral prosthesis surgical procedure to enable the surgeon to test the fit of a prosthesis with the trial components before actual implantation of the prosthesis. An example of a femoral prosthesis trial fitting device is described in U.S. Pat. 4,135,517 to Reale. This patent discloses a trial head 30 and a bearing insert which removably fits within the trial head. The bearing insert may be removably mountable on either a femoral prosthesis stem or a trial handle. Different sized trial heads may be utilized with this device.
Many provisional hip components utilize a single or one-piece provisional portion which is fitted to the spherical head of a hip stem implant or trial stem. Various sized single provisional portions are available. Such a provisional system is sold by Zimmer, Inc. for use with their BiArticular II Hip (a bipolar prosthesis). The BiArticular II Hip Prosthesis corresponds to the U.S. Pat. No. 4,770,658 to Geremakis et al., identified above.
In addition to utilizing a trial prosthesis, it is typical to utilize an acetabular sizing instrument for properly determining the size of the acetabulum. An example of such an instrument is disclosed in U.S. Pat. No. 4,528,980 to Kenna which includes an acetabular sizer which includes viewing ports in the shell for visual inspection of the acetabulum while the shell is seated therein.